1. Field of the Invention
This invention relates to the field of trimming trees and branches and more particularly to a device for trimming branches.
2. Description of the Related Art
As trees and shrubs grow, it is important to regularly trim them to keep them healthy and well groomed. Trimming is performed by cutting dead branches or branches that have grown too much or irregularly.
There are many trimmers already in use in the market. The simplest trimmer or hand tool has a pair of cutting blades similar to a scissor. Often the cutting blades are curved to improve cutting action, especially for green (wet) branches. A user opens the blades, surrounds the branch to be cut and applies force, closing the handles and cutting the branch.
A modified pivoted hand tool is described in U.S. Pat. No. 5,697,159 to Linden. This hand tool is an improvement over the common everyday prune tool. In the described hand tool, the lower handle rotates as the handles are compressed between the user's palm and fingers. The purpose is to improve leverage and comfort when cutting branches close to the user. The described hand tool works well for smaller branches when they are located within reach of a person using the tool, but is not adequate for larger branches or when the branches are out of reach of the person using the tools.
In response to this need, several extension tools have been deployed that let the person using such cut branches that are outside of their unassisted reach. One example of such is described in U.S. Pat. No. 3,584,381 to Jamison. The described tool has an extension handle that has an inner shaft within a pole. The pole is coupled to one cutting blade and the inner shaft to the other so that pulling or pushing the inner shaft with respect to the pole opens and closes the cutting blades. The inner shaft is connected to a hydraulic cylinder that is connected to a fluid pump. This tool is heavy and includes an expensive and complex system of extension poles, motors and hydraulics.
Another solution to the problem is presented in U.S. Pat. No. 4,707,917 to Westover, et al. The tool of this patent uses rotation of the extension pole to turn a screw that urges a base member to push the branch against a cutting blade, much like having the branch and a cutting blade in a vise. This tool requires many turns of the handle to move the base member far enough to cut a branch and has a release arm so the user doesn't have to turn the handle the same number of turns in the opposite direction in order to re-open the tool. This tool is not efficient when cutting many different branch sizes, especially for smaller branches which require the most number of turns of the handle.
Another pruning device is described in U.S. Pat. No. 5,960,546 to Cooke, et al. This device has a hollow extension pole with a cord or wire passing within. The cord is attached to the cutting system so that, when the extension pole is held stationary and the cord is pulled, the cutting blades engage and cut the branch. This device requires two handed operation, one to hold the extension pole and the other to pull the cord. Because of a lack of leverage, it is often difficult to support a heavy extension pole with one hand while using the other hand to pull on a cord.
What is needed is a simple pruning device that can cut various sized branches or other objects with simple mechanical movement.